Railway braking apparatus



Marh 27, 1945. H. c. cLAusEN ET AL RAILWAY BRAKING APPARATUS Filed Nov. 27, 194,3

Patented M'ar. 27, 1945 RAILWAY BRAKING APPARATUS Harold C. Clausen, Penn Township,l Allegheny County,V and Lnnie K. Hedding, Wilkinsburg, Pa., assignors to The Union Switch & Signal Company, Pennsylvania Swissvale, Pa.,

a corporation of Application November 27, 1943, Serial No. 511,980

l(c1. soa- 4 Claims.

Our invention relates to railway braking apparatus, and particularly to braking apparatus of y the type comprising wheel engaging braking bars located beside a track rail and movable toward and away from the rail into braking and nonbraking positions. More particularly, our invention relates to apparatus of the type described in which the braking bars are arranged to be moved to their braking positions .by a fluid pressure operated motor and to be restored to their nonbraking positions by suitable biasing means such as gravity.

In one form of braking apparatus of the type described, the admission of fluid pressure to, and the exhaust of uid pressure from, the fluid pressure operated-motor is effected through the medium of inlet and exhaust magnet valves, respectively. `These valves are energized over a plurality of control circuits, one of which is provided for the inlet valve and another of which is provided for the exhaust valve for each braking pressure desired, and each of which circuits includes a contact operated by a Bourdon tube subjected to the motor pressure. The circuits are "so arranged and the Bourdon tubes are so adjusted that for each control pressure for which provision is made the contact included in the circuit for the inlet valve will automatically operate to energize or deenerglze the inlet valve according as the motor pressure is below or above a predetermined pressure, while the contact in eluded in the companioncircuit for the exhaust valve will automatically operate to energize or deenergize the exhaust valve according as the motor pressure is above or below a predetermined pressure which is slightly higher than the pressure at which the contact for the inlet valve operates, whereby the pressure in the motor cylinder will be automatically held within preselected limits for each braking pressure provided for. With the circuits arranged in this manner when the pressure in the motor cylinder approaches the critical value at which the Bourdon tubes operate the associated contacts, a point is sometimes reached where the contact pressure is very light, and this fact coupled with the inherent resiliency of the Bourdon tubes gives rise to a condition generally referred to as valve flutter in which the magnet valve controlled by the contact is caused to become alternately enerand deenergized until a condition of equilibrium is linally reached. This so-called valve flutter is undesirable, and one object of our invention is to provide an arrangement of control circuits wherebyy the flutter can be eliminated of rail I.

and still affect the desired control with a minimum number of circuit wires.

According to our invention, we connect a condenser across the terminals of the magnet valve, and in order to permit the use of a preferred type of condenser we arrange the control circuit so that the polarity of the current supplied to the inlet magnet is the same for all of the control circuits which are provided for the inlet magnet.

-We also employ asymmetric units in a manner which enables certain of the circuit wires to be used in more than one of the control circuits.

Other objects and characteristic features of our invention will become apparent as the description proceeds.

Apparatus embodying our present invention is an improvement upon that shown and described in Letters Patent of the United States No. 1,947,638, granted to Herbert L. Bone, on Febru- 'ary 20, 1934, for Railway braking apparatus.

We shall describe one form of apparatus ern bodying our invention, and shall then point out -jacent pair of the usual crossties 3, only one crosstie being visible in the drawing. Associated with the rail I is a car retarder comprising two braking bars AI and A2 located on opposite sides Each of these braking bars comprises, as usual, a brake beam 4 and a brake shoe i5.

The braking bars AI and A2 are arranged to be moved toward and away from the rail I through the medium of a lever 6 which is pivotally mounted at one end on a pivot pin 8 carried by the rail support 2, and a lever 'l which is pivotally mounted intermediate its ends on the pivot pin 8. The lever Bis inclined upwardly and extends away from the rail I and. is provided in its upper surface with a groove Ea which receives the braking bar Al. The one end 'la of the lever 1 is likewise inclined upwardly and extends away from the rail I at the opposite side of the rail from the lever 6, and the other end 1b of the lever 1 is inclined downwardly and extends away from the rail I below the lever 6. The end 1a, of the lever 'l is provided in its upper surface with a groove lc, similar to the groove 6a in the lever 6, which groove receives the braking bars A2. The parts are so arranged and so proportioned that if the outer orfree ends of the levers Ii and 1 are moved apart, the braking bars will be moved toward the rails into their eiective or braking positions. When the braking bars occupy their braking positions, the brake shoes will engage the opposite side faces of a car wheel traversingrail I, and will retardfthe-speed ofthe car. The' center of gravity of the lever I and braking bar AI is considerably to the left of the pivot pin 8 so that this lever will normally tend to rotate ina counter-V clockwise direction about the pivot pin. Simi--v larly, the center of gravity of the lever 'I and braking bar A2 is to the right ofthevpivot-'pin'so that this lever will normallyv te'nclxto rotate iri a? clockwise direction about thepivot'pin. Itwill be apparent, therefore, that when no force is applied to the free ends of the levers 6 and I to move them apart, the free ends Vof-these levers" will move toward each other, thereby moving thebraking bars to their ineiective or non-braking position-iin whichfthey are illustrated: in the drawing.

The levers "5 and' 'I are-'arranged .to"be1 moved apartbymeans of a fluidfpressure' motorM com; prising 'r a cylinder I 9A containing i aI reciproca'ble piston'I Ilf'whichr is 'attached to' the linner-end'of" ay piston rodi x:I I."v The vcylinder 9 is" 'pivotally con"- nectdwith-tlefree endpf thelever vby means"4 of 'trunnions I2 formed onthe'sideof the cylinder 30' andfiextendin'g throughI bifurcations I3 formed on thefleve'rfywhil'e the piston "ro'dI I is connected," at its vf'een'd withthe free end 7h '0f 'thelever 'T by "means 'ofA an adjust'abl'e ey'e'b'olt" I I` and"-4 pivot pin 1521 Fluid-pressure :mayfbe admitted -f'to cylinder 9 between the upper endfof'th'e A"cx'flinder" forced'jdwnwardl'y"andthe 'cylindrf 'fupwardlif thereby separating the `levers 6 'and "1," and 'hence moving-th braking bars 'toward their effective br braking positionsl It"will'b`e1obvious that when'V thebaking barsfare moved to 'their braking' posiportional to the pressure of the uidsuppliedrto" the-cylinder 9.'

Th-supply vof huid pressure 'tothe cylinder 9 of" motor M is controlled vbymeans of two 'uidpres-r sure `operated `p oppet valves'22 and'23," which' poppetvalves, in' turn, are controlled by'means of"two vmagnet valves VI and V2.' Thesemagnet' valves f are similar and each comprises a' valve` stern I8 biased to an upper position by, means of a spring `I9`,"andfprovided with a winding 20 and an armature 2l. When valve VI is energized," as shownin the drawing,'valve stem I8 of this'valve moves downwardlfv against the bias exerted by the associated spring I9, and under theselcondi tions 'aspipe '24 is1 `connected with'a pipe 28`wh'ich' is constantly supplied with fluid pressure, usuel-lli'T compressed air, froma'suitable source not shownv intledrawin'g, When'valve VI is de'energized," howeve'rfpipe 214 is disconnected 'from pipe 28 and is connectedfwith .atmosphere through'a port 52'.'

When. .valve V2. is. energized, .valve stemV I8 ofm this valve moves-downwardly, .and .connects the pipe 28With a pipe-r2butvwhenvalve V2 -is deen-v. ergized; as shown-` in the drawing pipe-'728 is :disconnected `from the-pipefZQ and is-connecte`d withy atmosphere Pthrough a rport 3 I-.

Thetw fluid pressure'operated-fpoppetr valvesf 22 and-23 are both'l'ocatedfinthesamevalve body' 32,1an`d associated'with each poppet-valve is` spring 22a or 23a which constantly biases the valve to a closed position. Formed in the valve body 32 above the valve 23, and' in axial alignment therewith, is a cylinder 33 containing a reciprocable piston 36 which is operatively con nected with the valve 23. The upper end of cylinder `33 4is connected withfthe previously referred to pipe 29, and it Will be apparent, therefore, that when valve V2 is deenergized so that pipe 28 is cylinder 116* containingafzreciprocable pistonll' which is" operatively connected .with the 'valve 2 2 and. the' :upper iside of which: isisubjected :to the pressure inthefpipe 24.-` When valve VI isener-y gized;othegfluidrpressure which 'is then" supplied to"pipef24fforces1pistona rto its lower position thereby: opening 'valve '22,. andl under these conditions; cylinderl 9 of motor SM becomes connectedv withv atmospherenthrough;pipes ,I I and Q l cham# ber 52, valve 22, a chamber 4l formed .inlvalve4 positionglthus disconnectingoylinder.S from. at-

inospherelf It 'followszffroinctheEforegoing thatwhenwalve with* atmosphere.'-

The valvesfV i and VZ'are controlledy in part by a plurality-of 'pressureresponsive devices P20-323,

PIM-A55, andvP'lIl--lfeach* comprising a 'Boure don tubev25 jconnected :to'the'pipe' II,f'and'hence subjected to'thepressure'of the' fluid in the region of-cylinderf!! betweenpi'ston I 'and' the upper "end ofthe1cylinderx Eachy Bourdon tube-'25 controls twocontacts 2id-'Morand '2B-2612: The pressure responsive devices yP20'-3,-'P55551 and Pill-80 areso constructed and-'so adjusted that they'will operatesuccessively `as 'thepressurein the 'region of cylinder lSibetween' the lpiston IIl andthe upper end-or the-cylinder increases.V For' exampleiorv all,-pressuresrbel'ow 20 pounds per square'inch, the" contact l2 Eef-26a cfr-each ofv these devices yis closed.A If thepressure: exceeds 20 `poundsfper P2Ile'30 4opens;- .and f if the pressure" exceeds' 30 poundsper square inch, contact 25-235 of 'device 1320;*391y closes* InY asimilar manner, thev pressure responsive devicesPe-B and 'Pl @L-S are ad-jiuste'd toiopen their contacts26=-2 @a at 45 andl i 'mfpounds per square inch; respectively.` and to tacts.-.eaenrdesignated. loygsthed'eerence character; 21jwitltla,distinguishingesub'script cc-rresppudine.,ly to` ,theeppsitiom of the,-;;lever;;in .Whiclm: vthe .,corree spendi-ngi.. contacttiswclosed. Flor r example; conv etc.

Lever L .will..usually berlocatedeatta pointuemote. from. .thebrakingiapparatusl as. is..the. comi n trol.cabineoifatclasscation yardi caioretarderA 1'0 systermnand. will :be :connectedmwith .thes braking; apparatustoyQmeans of. line-...wires.-.extendingg from: thel; controlflcabin. te the: brakingr apparatus. As shown inthe-drawings lever. L.,oocupies its-pifr or Poli position-..vwhich .-is;..theipositien-. which: it 15 normally occupies when no cars areetonloe reeY tarded.,rand all of .the contacts or. fleversrhvvith the exception-.effi contacta 2I+"IJ are ther-etere-A opentA Valve ..V2 .is thereforeedeenergizedt butfyalue/Vl sise' energized over arcircuiuwhich passes ironm-a.suit 20 ablesource ci current such. asa .-battery; C.throu:gh;= linerwirel, the Winding'ot val-ve;VI; Wires;v 493i, 3 5 and...34, an4 asymmetrc..unit RI -in-"xbs lo-wuref sistancedirection, linewire'yand contact '21e-I i of lever.- L..loack..to loatteryfC. SinceffvalveN-Z is 25 deenergized, pipe 2li-Af is disconnected.; fromfpipef 2 9andethesupply". o l fluid pressure tot cylinder 9 is'..therefre,.cut o1\,,and since! valve-N1 iis-,eueregized; cylinder. 9 .is connected .withl atxfnesfp-lmere.:` l

The-.brakngybfars arerthereforefheldrfintheir in. l im 'Ihe-l.- apparatus also. includessae condenser, De 35 whichlis'connected. across the windingl @twelvev V2?. Tliiacondensenmayfbe ofanyysuitableetypey, but ispreferablyf an electrolyticw condenser f befcause electrolytic condensers are smaller and.`

movezfsthe brakingl` bars tto :theineiectiveeorzzlar ing ppsitions'.. Asfgsoon'fasfthe pressure inthe;-E

upper end of cylinderr reacheseZOepoundssper:

. wil'lllthent become-s; deenergizedatlrus .caueing.;valve 23 i to becomewclosedil.andehenc Ycuttizfrge: o.: the.V supply ot uid pressureatorftlreeupperiencliofxthez; cylinden until\.',tlfiel pressure4 inthe-:motori again; decreases `b'elovviV 20%. poundsi per -f square'f inclr` ati.. whicm time the:` resultanti reclosinge oi.: Contact.` 26e-26a ofndevee B20-3uwil1xrcausefvalveuV-Z to againn becomes energized# andi again.V open-i valve: 2 3st@ freaclmid: .fluidi fpressurerteitlrec motor: If three ilu-id inthee Imotorrnow` increases-gto:awpressure :of i 30ipoundslzperfsquarefinch zfrany.:I reason-,1 com. l tact.' 26e-26e ofi' pressures. responsivefz device--` P20L--30ewil-l become closedzand wiflbcompletee circuit. for valves; Vix passing'. from", battery tir-rough con-tact 21"-2-ot-'leverllp linecwire 385;. contaet4 261.926?) ofpressureiresponsive. device.l P20=+30nwires i134; 35-an`di49;i.the winding Zloi` valve/1.A VJ i andlinefA Wire# 3.7".- baeki to.. battery.Y B6. Valve- Vil i Wil'lx'therefree become energized-i ande' will: cause 'f valyeff 22 ftor: opens. thus venting. fluid# from cylinderzxt Valv'e'f-.ZZ .wil'lucontinueite venti: fluid..fronmcylinderi'llziuntil theifpressurein cyl-.

indem 9th-ass. decreasedxto '1301 poundsfrper squarelf inchi;A .Whereuporrv contact 2 6+-26btwill open.` Wli'eni thisehappeusavalveVl will. become deenergized andriwilfla-causezvalvee2 2 tto., close; thus 'preventing further escapero.fflfuidifromylinderfet It will' bien seem tllereorf- ,'f tlrattwl'ren-.leverflll occupies@ its phposition; the-ebrakingeibars; will Aloe neldflinxtheiri brak-1mm positonse ley:` ai., pressure of; between; 2Q@ and'pcundsper;squarciinchf.:

Ifwtheea:operatomdesiresstof make'latenterepovverJ fulbrakecapplieatioml're '.-wiilimove -lever :Lf tof its cheaper than; otheri types .forxa. given icapacity; 40.103m0st10n imwmoncontactz 21a-Skis' closed. Une..

'Ilf'eefunctien of the' fcondenser. D.- will bef-.1made;z clear.. asthef descriptionv proceeds In. explaining the.;operation.` ofthe-:apparatus: as.. a ,vs/hole, 1,.,shall assume-.than the: operator.:-

wishes to.makev a comparativelmlight lcrakeiapr 45 plication. Todo this, .hetmovesr leverfL. fromzits pl `to..its p2.. position, vthereby-J opening Contacti 2T--I 'of lever L' and closing contact,2l'-2.-;, Thea opening oi. Contact 2 l--i interrupts; .y the.;A circuitI which was. previously; closedeforvalveevd at.. this;VX bu y contactnand .valve V-l 'therefore 'fnowrbecomesledee energizedw and.. disconnects.. pipe. 24 from:Y piper- 28land..connects.pipe-.'24wwith atrnosplnere'.I When; f pipe ..24 becomes, connected; withb atmospheres: ,there pressure in this pipe and in the upper encliof.v o5

cylinderllt` decreases rapidly,- and.as..soon..as.this pressurehas decreased to a predetermined. value,

for example, 15 pounds per squareinch, spring 222i closes 1 valvew22j` thus disconnecting, cylinder.

` 9 from' atmosphere:l Tlie'cl'singofcontact 21;-22260 R2* in'.y itsr` loWl resistance direction, vWire 50," the i* (1,3.-

winding 2 Ilof valve V2* and'condenserD` -in ,mul-.l tiple;w and iline"wre31"back to batteryBI Valve. V2 itherefre becomes energized and connectslpipe. 28vvith pipe l29"so'tlat fluid "at fullllie pressure?.

is nnovvsupplied to the' upper end`.ofcylinder-T0.u

33;" thus' causingpis'ton 36 to. move'. downwardly. and bpenzvalve23. As was previously .pointed out, Whenvalve.. 231is ,.opened, piper 28'., becomes Y cor-rr nected 'withpipe I 1;' ,andiuidiatQ-full. .ilinenprese sureis therefore newsuppliedto. cylinder. 9to.

derrtliesefc'ondtonsvali/ew I vwill beedeenergizecl* andewalweiVZ wilt become energized'overra circuitj which?. passes; from: battery* B? through contact". 21e- Bief zleverlli,.linefvvire-` 43,@ con-tactf-Za' off pressure.; responsivec device: PM2-55; Wire`A 40;'- asymmetricmnit@Rhum its :lo-vvl resistance; direcLW tion; Wireclln condenser ."D,f. andthe winding 2U off. valyeeV. :inimultiple and `lineWireu3-l' `to bateteryfli. Eluirt pressure wi'lll therefore' nowf'be admitted 'tm-thee upper endfl ofE cyliriderf 9 until therpmessurefofitheffluiclfin"tlreecylinelrincreasesv me45,poundsmerisquaretinch :at which? time conM tact'. 25e-26m of pressure: responsive devicev P45=55awill.\operr and Willldeenergize vvalve V2 If l thee pressure: inf. the:` upperi end off? cylinder 9N noweincreasesitor :pounds persq-uare ineh; conv tact ZB-Z-Bbot pressure:responsivefdevicePfl55-55 will: ibecomeaclosedlanld willllcompleteianctlier circuit :for valveuVil i this latter-"circuit passing 'from' battevryu-Bthrcngh? acontact MFV-32eri leverA L', line- Wir-.e3 354 contact'f: 25e-261i?? 0in' pressureA responsive devioeffPA R455; Wires 1 iban'df 495 winding Zllicf valve V'l andrline wire 31 fbackttefbatteryfB; The:l resultant ienergization ofI ivalv'eVl will 'cause 'valve' i 22.:to.;=.open;. thusvexlratistin'gflui'dfrom theupper enst of cylinder:` 9*@ in 1 a manner 7Wlncicli will'l be" readily un'derst'codifrom the foregoing descriptions. Valve.: VI will ncwtremain *A energized `until their pressures hasridecre asedi to below# 55"- pounds per. squareeinch attvvl'liclnA` time Contact 2K5-28D of.. pressure eresppnsiveedevice; PA 5-55"w.i11i openi i' anclnwill intufrupat'fthe circuitffor VareVl Valve:4 221-` Will.,tlrerifreelose'z andwcut f; oifzth'e. furtlierfeXI-:- hanst Y oafluidafromicylinderr9: It will be .1 apparml ent,,therefore that LwhemleverzL occupies-its np3?.

position, the braking bars will be held in their braking positions by a pressure of between 45 and 55 pounds per square inch.

If the operator moves lever L to its p4 position, valve V2 will then become energized over a circuit which passes from battery B through contact 21-4 of lever L, Wire 44, Contact 2'6-26a of pressure responsive device PTD- 80, asymmetric unit R2 in its low resistance direction, wire 50, condenser D in multiple with vthe winding of valve V2, and line wire'Sl back to battery D. Under these conditions fluid will be supplied to the upper end of cylinder!! until the pressure in the cylinder reaches 70 pounds per square inch, which is the pressure at which contact 2li-26a of pressure responsive device P10-8i) opens. If the pressure in cylinder 9 now increases to 80 pounds per square inch, contact 26-266 of pressure responsive device P10-89 will become closed and will complete still another circuit for valve Vl. This latter circuit for valve VI may be traced from battery B through contact 21-4 of lever L, line wire M, contact 26-261) of pressure responsive device PTE- 89, wire 49, the Winding 20 of valve VI and line wire 3l back to battery B. Valve VI will therefore become energized and will cause valve 22 to open until the pressure in the upper end of cylinder 9 decreases to 8O pounds per square inch. It will be seen, therefore, that when lever L is moved to its p4 position, cylinder S is supplied with iiuid at a pressure of between 'l0 and 89 pounds per square inch, so that the braking bars exert a corresponding braking force.

It should be particularly pointed out that whenever valve V2 becomes energized with lever L in any one of the positions previously described, the condenser D becomesr charged, and, as a result when this valve subsequently becomes deenergized due t the opening of the co-ntact 2li-26a of any one of the pressure responsive devices P20-3U, P45-55 or Pill-89, the condenser discharges through the winding 2li of valve V2. Furthermore, the condenser provides a shunt path for any current which may be induced in the winding 20 due to the decaying ux in the magnetic current of the magnet valve, whereby the valve V2 is caused to remain closed for an interval of time after the contact 2li- 25a opens. The length of this time interval depends upon the proportioning of the parts, and the parts are preferably so proportioned that sufficient iluid will be admitted to cylinder 33 at any time after the contact 2li-26a which is then effective to control the energization of valve V2 opens, t0 cause valve 23 to open and admit enough fluid to the cylinder 9 to prevent this contact from remaining in an unstable state Where it will cause the Valve to flutter, but that, this iluid will not be sufjcient in volume to cause the associated contact 'IE6-26h to become closed and energize valve V! to vent fluid to atmosphere.

It should also be particularly pointed out that when lever L occupies its p2, p3 or p4 position valve V2 is always supplied with current of the same polarity, so that it is possible for the condenser D to be of the electrolytic type. This is an advantage due to the smaller size and less cost of this type of condenser for a given capacity.

If the operator desires to cause the braking bars to exert their maximum braking force, he moves lever L to its p position. Under these conditions valve V2 becomes energized and subsequently remains energized over a circuitwhich passes from battery B through contact 21-5 of lever L, line wire 30, wire 50, condenser D in multiple with the winding of valve V2, and line wire 31 back to'battery B. The energization of valve V2, of course, causes valve 23 to open, and when valve 23 becomes opened, fluid at full line pressure is supplied to the upper end of cylinder 9. It will be apparent therefore that under these conditions the braking bars will be held in their braking positions by fluid at full line pressure.

It should be observed that if the operator moves lever L from a position corresponding to a higher braking force to a position corresponding to a lower braking force, the apparatus immediately and automatically reduces the braking pressure to a value corresponding to the' new position of the lever in a manner which will be apparent from the drawing without tracing the sequence of operation in detail.

When lever L occupies any one of its p2, p3, @il or p5 positions, so that the braking bars occupy their braking positions and the operator wishes to restore the braking bars to their non-braking position in which they are illustrated in the drawing, he will restore lever L to its pl or oir position. When he does this, all circuits previously traced for valve V2 will be interrupted, and the circuit previously described for valve Vl including contact Z'I-l of lever L will become closed. Valve V2 will therefore become deenergized and valve Vl will become energized thus l causing valve 23 to close and valve 22 to open,

As a `result, the supply of fluid pressure to the upper end of cylinder 9 will be cut off, and the uid which was previously supplied to this end of the cylinder will be ventedto atmosphere. The braking bars will therefore move under the iniiuence of gravity to their ineiective or non-braking positions. When the braking bars reach their non-braking positions, all parts are restored to the position in which they are shown in the drawing.

It should be particularly pointed out that the use of the asymmetric units Rl and R2 in the circuits for the valves VI and V2 in the manner described enables the number of line wires required between the lever and the retarder to be reduced to a minimum and at the same time makes it possible to arrange the circuits so that valve V2 will always be supplied with current of the same polarity.

Although we have herein shown and described only one form of railway braking apparatus embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is:

l. In combination, a fluid pressure motor, a pressure responsive device subjected to the pressure of the fluid in said motor and provided with a rst Contact which becomes opened or closed according as the pressure of the fluid in said motor is above or below a first predetermined pressure and with a second contact which becomes closed or opened according as the pressure of the fluid in said motor is above or below a second predetermined pressure somewhat higher than said rst pressure, a first magnet valve eiective when energized to cause fluid to be admitted to said motor, a second magnet valve effective when energized to cause uid to be exhausted from said motor, a pair of manually operable contacts, a pair of line wires, two sources of electromotive force one effective to supply said line wires with current of one polarity and the other effective to supply said line wires with current of the other polarity according as the one or the other of said manually operable contacts is closed, means including said first contact and a first asymmetric unit poled to pass current of said one polarity only for connecting said first magnet v'alve with said wires, means including said second contact for at times connecting said second magnet valve with said wires, and means including an asymmetric unit poled to pass current of said other polarity only for at other times connecting said second magnet valve with said wires.

2. In combination, a fluid pressure motor, a pair of line wires which are reversibly supplied with current, a pressure responsive device subjected to the pressure of the fluid in said motor and provided with a first contact which becomes opened or closed according as the pressure of the fluid in said motor is above or below a first predetermined pressure and with a second contact which becomes closed or opened according as the pressure of the fluid in said motor is above or below a second predetermined pressure somewhat higher than said first pressure, a flrs't magnet valve effective when energized to cause fluid to be admitted to said motor, a second magnet valve effective when energized to cause iiuid to be exhausted from said motor, means including lsaid first contact and an asymmetric unit poled to pass current of one polarity but not the other for connecting said first magnet valve with 'said wires, means including said second contact for at times connecting said second magnet valve with said wires, means including an asymmetric unit poled to pass current of said other polarity for at other times connecting said second magnet valve with said wires, and a condenser connected in multiple with said first magnet valve.

3. Railway braking apparatus comprising a braking bar located inthe trackway beside a trackl rail, a fluid pressure motor for moving said braking bar toward the'track rail into a braking position in which it will engage a part of a car to retard the speed of the car, .a first magnet valve effective when energized for connecting said motor with a source of fluid pressure, a second magnet valve effective when energized for connecting said motor with atmosphere, a lever having an off and a plurality of on positions, two sources of fluid pressures, a plurality of devices responsive to the pressure of the fluid in said motor, each said device being provided with a first contact which is opened or closed according as the motor pressure is above or below a first predetermined pressure and a'second contact which is closed or opened according as the motor pressure is above or below a second predetermined pressure which is higher than said first pressure, `said devices each being'responsive to predetermined pressures which are different from the pressures at which the other devices respond; a first energizing circuit for said second magnet valve including a first one of said sources, a first contact of said lever closed only in the ofi position and an asymmetric unit connected to pass current 'of the polarity of said first source; a plurality of other energizing circuits for said second magnet valve each including the other source of current, a. contact of said lever closed in a different one of one of the on positions of said lever, the first contact of a different one of said pressure responsive devices, and an asymmetric unit poled to pass current of the polarity supplied to said circuits by said other source, said first energizing circuit including certain of the wires included in the other circuits for both magnets and said two sources being poled in the opposite directions in the respective circuits in which they are included.

4. Railway braking apparatus comprising a braking bar located in the trackway beside a track rail,.a fluid pressure motor for moving said braking bar toward the track rail into a braking position in which it will engage a part of a car to retard the speed of the car, a first magnet valve effective when energized for connecting said motor with a source of iiuid pressure, a second magnet valve effective when energized for connecting said motor With atmosphere, a lever having an off and a plurality of on positions, two sources of fiuid pressure, a plurality of devices responsive to the pressure of the fluid in said motor, each said device being provided with a first contact which is opened or closed according as the motor pressure is above or below a first predetermined pressure and a second contact which is closed or opened according as the motor pressure is above or below a second predetermined pressure which is higher than said first pressure, said devices each being responsive to predetermined pressures which are different from the pressures at which the other devices respond; a first energizing circuit for said second magnet valve including a first one of said sources, a first contact of said lever closed only in the off position and an asymmetric unit connected to pass current of the polarity of said first source; a plurality of other energizing circuits for said second magnet valve each including the other source of current, a contact of said lever closed in a different one of the on positions of the lever and the second contact of a different one of said pressure responsive devices; a plurality of energizing circuits for said first magnet valve, each including said other source, a contact of said lever closed in a different one of the on positions of said lever, the first contact of a different one of said pressure responsive devices, and an asymmetric unit poled to pass current of the polarity supplied to said circuits by said other source; said first energizing circuit including certain of the wires included in the other circuits for both magnets and said two sources being poled in the opposite directions in the respective circuits in which they are included, all of the circuits for said first magnet valve being arranged to supply said first valve with current of the same polarity, and an electrolytic condenser connected across said first valve in the direction to become charged when said first valve becomes energized, whereby valve flutter is eliminated when said first valve becomes deenergized due to the operation of any one of the first contacts of said pressure responsive devices.

HAROLD C. CLAUSEN. LINNIE K. HEDDING. 

